1. Field of the Disclosed Embodiments
This disclosure relates to systems and methods for implementing performance improvements in a multicast protocol in instances of packet loss in the network during time-correlated blockages.
2. Related Art
The Internet has become highly dependent on congestion control mechanisms, and particularly Transmission Control Protocol (TCP) congestion control mechanisms, that allow data streams to share bandwidth fairly. Widespread deployment of a transport protocol that does not interact gracefully with the TCP has the potential to raise significant difficulties. These difficulties were once considered an obstacle to effective standardization of reliable multicast protocols.
The NACK-Oriented Reliable Multicast (NORM) protocol is designed to provide end-to-end reliable transport of bulk data objects or streams over generic Internet Protocol (IP) multicast routing and forwarding services. NORM uses a selective, negative acknowledgement (NACK) mechanism for transport reliability and offers additional protocol mechanisms to conduct reliable multicast sessions with limited up front coordination among senders and receivers. A congestion control scheme is specified to allow the NORM protocol to fairly share available network bandwidth with other transport protocols such as TCP. It is capable of operating with both reciprocal multicast routing among senders and receivers and with asymmetric connectivity (possibly a unicast return path) from the senders to receivers. The protocol offers a number of features to allow different types of applications or possibly other higher level transport protocols to utilize its service in different ways.
When using a reliable multicast protocol such as NORM, packet loss due to time-correlated blockage at the physical (PHY) layer is interpreted as congestion loss by the receivers. The receivers then request the sender to throttle data rates on the assumption that there is congestion in the network. When there are multiple receivers that can independently experience blockage, the throughput of the NORM session goes down significantly leading to dramatic system underuse and consequent application performance degradation. NORM includes no built-in mechanism for ECN signaling on congestion.